The present invention relates to papers and similar substrates bearing embossed light-diffracting and holographic type fine line multi-color prism-like refracting surface patterns and images; being more particularly directed to novel methods of manufacturing such papers, boards and other substrates without requiring the laminating of decorative embossed-pattern surfaces thereupon, and to improved and less expensive single integral film or sheet substrates of this character.
The art is replete with processes for laminating thin sheets to paper and paper-like surfaces, including metallized layers, upon which patterns or images or other data have been impressed or transferred from surfaces containing such patterns or images or the like.
Coatings providing smooth and other surfaces and metallized film layers and the like have also been provided upon paper-like surfaces, and adhered thereto by ultraviolet (u.v.) and electron beam (e.b.) radiation-curable adhesive coatings, such as described, for example, in U.S. Pat. Nos. 4,490,409 and 4,246,297. The latter, for example, have been widely used for glossy decorative paper wrappings and similar applications.
Relatively recent interest in holography and in intricate light-refracting and diffracting surface patterns in general has enabled the producing of unique multi-faceted varied color surface effects on paper, board and other substrates that not only are highly decorative but, for important useages where duplication is not desired (currency, stock or bond certificates, credit cards, etc.), cannot be faithfully copied on xerographic reproducing machines, or otherwise easily counterfeited. The prior art layering or laminating of light-diffracting films or layers to paper or other substrates, and similar processes used to achieve these results, however, are relatively expensive and require multiple steps of fabrication.
The use of metallized papers, adapted for printing, has been expanding for a variety of applications, including printable product labels and the like, and with the high-quality glossy decorative appearance rendering them most desirable also for gift wrappings, packaging, gift bags and other uses. Light interference surface effects have been produced by embossing fine lines into a coated layer on paper and then metallizing the embossed surface to give rise to prism-like multi-color refraction and diffraction effects, producing predetermined patterns and images, including holographic images, where desired, and that present changing shiny, multi-color mirror-like effects at different viewing angles.
Such papers have heretofore been produced by applying a thin layer of pre-lacquer to the base paper, drying the lacquer to a hard finish, and embossing the lacquered surface by conventional embossing rotary metal dies, under heat and pressure. The dried paper is then introduced into a metallizing vacuum chamber where a very thin layer of aluminum or other metal (say 2 millionths of an inch or so) is deposited to metal-coat the embossed lines so as to provide a metallized light-reflecting line pattern, The metallized paper is then returned to the coater station where the paper is top-coated with a print primer and remoisturized, in view of the earlier layer drying, as described, for example, in the 1994 bulletin of van Leer Metallized Products of Franklin, Massachusetts, entitled Illuminations.
As further explained in the Van Leer 1996 Holo PRISM(trademark) bulletin, optimally to produce light-diffraction gratings and similar optically ruled or otherwise engraved or cut fine line surface patterns, a line spacing of the order of about 25,000 per inch will generate optimal prism-like multi-color light diffraction and holographic images or patterns and the like.
Underlying the present invention, on the other hand, is the discovery of how the appropriate use of e.b. curable adhesive thin layer coatings on paper and similar substrates, and/or u.v. in some cases, can enable the direct and inexpensive, but highly faithfully reproduced transfer of intricate diffracting-refracting and holographic surface prismatic embossings from thin flexible embossed film or web masters, and without requiring the use of any additional embossing metal dies, or separate fabrication steps, or top coats, or paper remoisturizing, or layer laminations on the substrates.
An object of the invention, accordingly, is to provide a new and improved method of directly transferring to paper, board and other substrates and the like, the fine-line patterns of light diffracting-refracting and holographic images, and with a relatively low-cost u.v. or e.b.-curable coating pattern or image transfer technique using preferably an appropriate flexible pattern-embossed film web master.
A further object is to provide improved diffracting, refracting and/or holographic products produced by such method.
Other and further objects will be explained hereinafter and are more particularly delineated in the appended claims.
In summary, however, from one of its important aspects, and where metallizing is not involved, the invention embraces a method of producing on a substrate surface predetermined multi-color diffraction-refraction effects and patterns, that comprises, applying between a flexible film master, provided with an embossed predetermined diffraction pattern formed of fine lines, and a substrate surface, a radiation-curable adhesive coating material of a type that, when radiation cured, will integrally bond to the substrate surface but not to the material of the embossed film master; pressing the flexible film master and substrate together with the coating interposed to cause the surface of the coating adjacent the embossed film master to become impressed with a faithful reproduction of the predetermined fine line diffraction pattern of the film master; radiation-curing the adhesive coating to set the impressed diffraction pattern in said coating surface upon the radiation-curing of the coating, while integrally bonding the coating to the substrate surface; and stripping the resulting integral diffraction-patterned coated substrate from the flexible film master.
The invention also is most useful where the film master has been metallized and the metal layer is adhered to the paper to generate even more spectacular shiny multi-colored effects.
Best mode and preferred embodiments and designs and products will hereinafter be more fully detailed.